1. Field of the Invention
The present invention relates to a machine for sealing cardboard boxes of constant width.
2. Description of the Related Art
Known machines for sealing cardboard boxes of constant width but variable width when passing from one series of boxes to another comprise a bed which describes a table for support and advancement of the boxes, a pair of pulling units placed at an adjustable distance along opposite sides of said supporting table to achieve a pulling engagement with the sides of said boxes, a lower taping unit and an upper taping unit arranged in a raised position which is adjustable with respect to the supporting table in order to seal the tops of the boxes during their advancement along said supporting table.
In the aforesaid machines it is important to ensure correct engagement of the pulling units with the sides of the boxes at the beginning of, during and at the end of the working travel in such a manner as to provide continuous advancement of the boxes and at the same time avoid damage thereto.
This requires in addition to appropriate devices for adjustment of the distance between the two pulling units and equally appropriate motorization devices for the belts, an effectively sliding assembly of the pulling units on guides capable of shifting said belts in a limited manner from their normally parallel positions in the loading and unloading operations of the boxes, but without abandoning the correct orthogonal position with respect to the supporting table. With the first movement by creating a slight convergence of the belts while the boxes are being fed and a slight divergence when they are being unloaded actually facilitates introduction and unloading of the boxes, the second movement would compromise effective pulling engagement with the sides of the boxes and hence their correct advancement into the working area.
As concerns the inlet ends of the two pulling units it has proven beneficial to equip said ends with supports mounted on sleeves sliding on a transversal guide bar fixed to the bed and coupled elastically to nut screws engaged in threaded portions of a distance-adjustment screw which can be rotated by means of a control crank. The elastic coupling with the nut screws ensures the appropriate working pressure for each distance adjustment performed by means of the regulation screw and made possible by the sliding of the sleeves on the guide bar.
The outlet ends of the pulling unit are in turn fitted with supports mounted on sliding sleeves on one or two transverse guide bars fixed to the bed and receive motion for the belts from motorized shafts which pass through said supports and are connected to a drive motor through a system of chains and gears. Otherwise the two functions of motorization and guide are simultaneously ensured by motion transmitting bevel gear pairs constrained in their rotation but freely sliding on a rotating drive shaft. In either case the outlet ends of the pulling units follow the adjusting motion of the inlet ends and allow shifting of the belts with respect to their normally parallel position to facilitate feeding and unloading of the boxes.